Regio- and Diastereoselective Synthesis of Substituted Triazolo [3,4-b]thiadiazin-6-ols and Triazolo[3,4-b]thiadiazines

Abstract An efficient, catalyst-free, regio- and diastereoselective approach for the synthesis of novel 7-aryl-3-alkyl(aryl)-6-methyl-6,7-dihydro-5H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-6-ols has been developed via the reaction of 4-amino-[1,2,4]triazole-3-thiols with nitroepoxides in methanol at room temperature. The products were simply dehydrated in the presence of PTSA in ethanol at 70 °C to afford the corresponding 7-aryl-3-alkyl(aryl)-6-methyl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines in 91–98% yields. In addition, treatment of the product with acidic chloroform afforded the corresponding α-((4-amino-5-methyl-4H-1,2,4-triazol-3-yl)thio)-α-phenylpropan-2-one in quantitative yield.